Effluent Treatment Plant Process in Textile Industry

Effluent in the artificial sense is generally considered to be water pollution, such as the outflow from a sewage treatment facility or the wastewater discharge from industrial facilities. In textile and wet processing industry use different types of dyes and chemicals in the operation of weaving, dyeing, printing, finishing and garment washing plant. This wastewater is treated in effluent treatment plant (ETP).

Fig: Effluent treatment plant (ETP)

Textile wastewater is the main source of organic contamination regarding pollution within the textile industry. Several cleaning processes may be used to remove organic pollutants from textile waste water. In general, we distinguish between physical methods (adsorption, filtration methods, coagulation and flocculation processes), chemical methods (oxidation, advanced oxidation, Fenton’s reagent) and more recently, more attractive biological treatment (anaerobic, aerobic) as an effective option for relatively inexpensive effluent de-coloration. Non-destructive physical techniques just transfer the pollutants to other mediums (sludge, concentrate in filtration techniques) and cause secondary pollution.

Process sequence of effluent treatment plant (ETP) in wet processing industry: 

Fig: Flow diagram of effluent treatment plant (ETP)

A typical sequence of operation involved for effluent treatment: 

Primary filtration
↓
Cooling & Mixing
↓
Neutralization by acid/alkali dosing
↓
Chemical coagulation
↓
Setting & separation of sludge
↓
Bio-degradation
↓
Again setting & separation of sludge
↓
Sludge pit
↓
Filtration
↓
Discharge to drain
Briefly described the above effluent treatment plant stages in below:

Primary filtration:
Waste liquor after pretreatment, dyeing, printing and finishing is subjected to primary filtration in which removal of gross solids, such as waste threads, fabric pieces, lint’s etc. takes place.

Cooling & Mixing:
After primary filtration, the liquor passes to cooling and mixing tank in which uniform mixing of effluents from various process takes place. A paddle mixer is provided for mixing. Cooling of the effluent may be done with the help of cooling tower.

Neutralization:
The effluent is pumped to a tank in which it is neutralized by acid or alkali dozing. The tank has an automatic dosing controller which at automatically control the dose of acid or alkali to maintain the required pH.
Coagulation:
Then the effluent is pumped to the coagulation tank. Chemical coagulation very effective for removal of color and suspended materials, aluminum, ferrous sulphates, ferric chloride, chlorinated copper etc. to increase the efficiency of coagulation, coagulation gain may be added for example polyacrylate.
Setting & separation of sludge:
Some of the soluble organic matter and light suspended solids will form a blanket of flocculent matter with the coagulants. The blanket is skimmed off to another tank and the remaining solution is moved to pressure filter.
Pressure filter:
For pressure filtration vacuum pumps may be used to force through the filter and suspended flocks are collected in the pressure fine filter.
Discharging to drain:
After filtration the purified water sent to drain which eventually reach to the river or anywhere else.